I don't recall it off the top of my head, but at least hid-lg.c, hid-lg.h and hid-lgff.c were modified as well, the device ID for DFGT also had to be added to hid-core.c. Unless you really have to use kernel 3.0 for some reason, stick with 3.2, otherwise I suggest you grab the whole patchset from git.kernel.org and apply it "properly" using patch utility instead of manually copying the updated sources.

EDIT: The patches were written against linux-next which at that time contained the 3.1 kernel (IIRC) so there is a slight possibility that the patches won't apply cleanly against 3.0

Thanks, but my point was that I "just" replaced the hid-ld4ff, nothing else. So, I wouldn't have been surprised if FF didn't work in the native mode. My problem is that it doesn't work at all now.

Secondly we have to make this work on many different machines. So, is there any way of getting 3.2.1 on them without compiling it for every machine separately?

It's a bit more complicated than that, patching just the lg4ff cannot possibly work (you're lucky it even compiles actually), if you read the source in the patches, you'll see why.
As long as your machines use the same distro, it shouldn't be a problem to create a package containing the precompiled kernel, refer to your distro's manual for details.

EDIT: Some distros like Ubuntu provide packages with the latest kernels.